As flow control devices, valves are commonly employed to regulate the flow of gases in a variety of machinery systems. One such application is to control the flow of air to adjust a lumbar support system found in seating systems in tractor trailer trucks. These lumbar systems typically include bladders that are inflated and deflated to adjust the lumbar support. For use in trucks of this nature, it is important that the valve be capable of performing as a high/low pressure valve to reduce the truck's supply pressure so as not to damage the bladder of the lumbar support during inflation. The operating air system of a truck of this nature is typically running in the range of 90 to 120 psi, and a conventional bladder has a maximum operating pressure of about 15 psi. Thus, it is necessary to significantly reduce the truck's pressure supply for use in the lumbar support of the seating system.
Further, valves used in seating systems must be reliable and durable enough to withstand heavy and repeated use. Therefore, for a valve to last at least five years, it must be durable enough to operate for many thousands of actuations.
Furthermore, these valves must be relatively compact for incorporation in the limited space allocated to seating systems. For instance, in a truck seating system, the control valve is typically located along the side of the seat below seating surface. Thus, the valve must be sufficiently compact in order to be effectively mounted for convenient operation at this location.
Moreover, in addition to these necessary functional and size requirements, cost is of significant consideration in vehicle seating design and manufacturing. It is important that the cost of each component of the seating support system be considered closely. As a consequence, the desired valve design would incorporate as few parts as necessary, while still meeting the durability levels and being cost effective to assemble and manufacture.
Slide valves are a common type of air valve being used to control the lumbar support of truck seating systems. A typical slide valve includes a slide mounted for linear movement in a valve body, and during operation, the passenger shifts the slide manually in one direction to allow air to flow through the valve to inflate the bladder and in an opposite direction to allow the air to flow to deflate the bladder. The slide is naturally biased to an off position to retain the latest setting for the lumbar support bladder. Typically, a coil type spring is used to provide the biasing force to automatically shift the slide linearly to the off position between the fill and vent position. An advantage of being biased automatically to the off position is that the operator does not have to consciously shut off the valve, which, consequently, precludes the accidental introduction and release of air as a result of a failure to shut off the valve. Examples of slide valves are disclosed in U.S. Pat. No. 5,447,178, issued to Gabrlik et al., on Sep. 5, 1995, and U.S. Pat. No. 4,524,951, issued to Green et al., on Jun. 25, 1985.
Rotary valves are another type of valve commonly employed for controlling air flow. A typical rotary valve assembly includes a valve disk mounted for rotation in a valve body. The disk includes a number of passages and rotates in the valve body to interconnect the passages to control air flow through the valve assembly. An example of a rotary valve is disclosed in U.S. Pat. No. 3,443,592, issued to Felmlee, on May 13, 1969, which discloses a spring for biasing a sealing arrangement between the stacked components, and not for biasing rotation.
A known shortcoming found with both the slide and rotary valves is the tendency to be relatively expensive to manufacture and assemble. This is due, in part, to the inclusion of a relatively significant number of independent, delicate components, including spring arrangements where the spring requires its own operating space adjacent the valve operator and preloading during assembly. Further, this renders the valve assembly bulky. Moreover, it has been found that these intricate valve designs are significantly more susceptible to failure, such as spring fatigue, and requiring repair or replacement.
Thus, the present invention is directed to providing a valve assembly which is less expensive to manufacture and that has a compact design with a more integral spring design that is durable and reliable in heavy use situations, such as tractor trailer truck seating systems.